This study concerns a prospective, longitudinal investigation of children with schizophrenic mothers, schizophrenic fathers, and two schizophrenic parents. As groups, these children are known to be at high risk for the eventual manifestation of schizophrenia. Propspective studies may therefore examine antecedent conditions and the pathogenic process relating to the development of the disorder prior to overt onset and without confounding by the effects and concomitants of the psychotic state. Long-term goals of this research are directed toward analyses of biological-environmental interactions, toward development of screening methods for early identification of vulnerable children, and toward instrumentation of preventive intervention programs based on a more firm understanding of etiological factors and the premorbid state. Emphasis will be placed on measures relating to possible neurophysiological dysfunctions. Attention will be given to factors that differentiate vulnerable and resistant children within the high-risk groups. A sample of 80 children with one or two schizophrenic parents, 25 children whose parents have nonschizophrenic disorders, and 100 children whose parents are not psychiatrically ill has been followed since 1971; the age range of these children upon initial examination was 7-12 years. Developmental data were also collected on 122 younger and older siblings of the target-age children. Most of the sample was re-examined approximately two years after first being studied, and a third round of examinations is in progress. A second sample of at least 135 7-12 year old children distributed across the several parent groups is now under study.